The present invention relates to propulsion control systems generally. More particularly, the invention relates to a propulsion control system that varies nozzle throat geometry to accommodate multiple propulsion phases.
Surface-to-Surface, Surface-to-Air, Air-to-Air, and Air-to-Surface missiles typically depend on two phases of propulsion. These include a high thrust boost phase and a lower thrust sustain phase. The former provides velocity and the latter sustains that velocity. Typically, such a two-phase propulsion system is accomplished with a two grain motor. However, among the drawbacks of multiple grain motor configurations is that there is only one nozzle throat which is optimized for one of the grains, but not both. As a result, there are large inefficiencies during one of the phases. Although pintle systems have been used in high performance rockets to vary nozzle throat area during flight to compensate for variations in combustion chamber pressure due to nozzle erosion and/or ballistic instabilities, for example, these systems have not been without limitation. More specifically, pintle systems generally involve complicated instrumentation, feedback control loops, and electric or hydraulic motor or squib actuation.